Details on the baby's gender, weight and name were not available. This is also the first child for Miller's fiancé, Tom Sturridge.
Miller, 30, and Sturridge, 26, have been dating for over a year and became engaged in February. Miller, who was most famously linked to Jude Law on-and-off for several years, will next be seen in the HBO TV movie The Girl, playing actress Tippi Hedren to Toby Jones' Aldred Hitchcock, who had directed her in The Birds. Sturridge next co-stars in On the Road, the big screen adaptation of the acclaimed Jack Kerouac novel.